1. Field of the Invention
The present invention relates generally to a display apparatus, and is directed more particularly to a display apparatus in which a first substrate and a second substrate, each having an electrode, are opposed through a spacer with a constant distance.
2. Description of the Prior Art
In the art, there are proposed display apparatus such as a liquid crystal (LC), electro-chromism (EC), electro-luminescence (EL), plasma (a kind of gas discharge) display apparatus and so on. These display apparatus have the construction generally shown in FIG. 1. In FIG. 1, 1 designates a first substrate (front panel) made of transparent material such as glass or the like, 2 a second substrate (back panel) made of glass, ceramics or the like which could not be transparent, 3 spacers serving to keep a constant distance between the first and second substrates 1 and 2, 4 a plurality of electrodes formed on the first substrate 1, and 5 a common opposing electrode formed on the second substrate 2, respectively. In this case, the spacers 3 are each made of, for example, ball-shaped glass beads or rod-shaped glass fibers. In the figure, 6 denotes light emitting or modulating material sealed in the space defined by the first and second substrates 1 and 2 which are sealed with each other by sealing material 7 made of resin or low melting point glass (frit glass).
With the above display apparatus, when a voltage is applied between a selected one of the electrodes 4 and the opposing electrode 5, light emission or modulation or coloring is generated selectively to present a desired display.
By the way, the performance (light emission start voltage rising-up and falling-down times and so on) of such the display apparatus depends mainly on the distance between the first and second substrates 1 and 2. For example, in the case of a gas discharge tube, the discharge initiate voltage is in proportion to the distance between the substrates, and in the case of a liquid crystal display apparatus (LCD), the distance between the substrates affects on the voltage response speed and so on with an error of about from several microns (.mu.) to 10.mu.. Accordingly, the flatness of two substrates 1 and 2 are required to be high. To this end, the spacers 3 are used to maintain the distance between two substrates constant (uniform). If the pressure in the space sealed by the substrates 1, 2 is rather lower than the atmospheric pressure, since the substrates are pressed by the atmospheric pressure, the spacers 3 reveal their effect. However, in the cases of EL, ECD, LCD and so on, the pressure in the space defined by the substrates is substantially equal to the atmospheric pressure so that the spacers 3 perform no effect. In addition, as the substrate becomes large, the above phenomenon becomes remarkable. Therefore, it is rather difficult to make a display apparatus having a large panel.
In the art, in order to make the distance between the substrates of the display apparatus uniform, such a method is considered that the substrate itself is curved or the substrate is urged. The method, however, each utilizes the elasticity of the front or back glass panel, so that the above method has the following drawbacks:
(i) When the substrate is curved too much, it becomes difficult to positively and sufficiently seal the substrates with each other; PA1 (ii) Pressure is concentrated at the central portion of the substrate; PA1 (iii) The quality and thickness of glass making up the substrate is limited; PA1 (iv) In case of frit-seal, distortion causes crack; and PA1 (v) When the substrate is curved, fine electrode pattern can not be formed because the electrode is formed on the curved surface of the substrate. PA1 (a) a first panel having an electrode provided on a surface thereof; PA1 (b) a second panel having an electrode provided on a surface thereof; PA1 (c) display material intervened between said electrodes of said first and second panels; and PA1 (d) a spacer disposed between said first and second panels, peripheral portions of said first and second panels being sealed by sealing material, characterized in that one of said first and second panels comprises a substrate and an elastic plate which is sealed to said substrate with its periphery, and fluid is sealed into a space defined by said substrate and elastic plate with such a pressure that said elastic plate contacts said spacer.
Further, in order to make the flatness of the substrate high, it may be considered to increase the thickness of the substrate. This, however, results in the increase of its weight. Further, the calender thereof becomes expensive.